Ice cores reveal historic heights of CO2

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Deep ice cores from Antarctica reveal there is more carbon dioxide in the atmosphere today than at any time in the last 800,000 years.

The data comes from analysis of tiny air bubbles buried 3.2km down in the Antarctic ice sheets. These provide a record of the ancient atmosphere and give insight into how climate was affected by CO2 levels in the past.

Dr Eric Wolff from the British Antarctic Survey explains: "Ice cores reveal the Earth's natural climate rhythm over the last 800,000 years. When carbon dioxide changed there was always an accompanying climate change."

He says over the last 200 years the concentration of CO2 has been increased beyond the natural variation, and that human activity is to blame. No one knows how the environment and climate will respond to this amount of atmospheric CO2, he added.

He told the BBC: "There's nothing that suggests that the Earth will take care of the increase in carbon dioxide. The ice core suggests that the increase in carbon dioxide will definitely give us a climate change that will be dangerous."

As well as unprecedented CO2 levels, we are also seeing the fastest rate of change in the concentrations of the greenhouse gas, Wolff added. Until very recently, the fastest rate of change was an increase of 30 parts per million over a thousand years. We have seen the same increase, 30ppm, in the last 17 years.

"We just don't have an analogue in our records," Wolff said.

The impact of further increases in atmospheric carbon could be wide ranging, the BAS says, beyond the well publicised potential to affect the climate.

Although the Earth has plenty of natural carbon sinks - places that absorb carbon - it is uncertain how effective these stores will be in the future. If carbon levels continue to rise, the oceans will have to absorb more and more carbon, and as a consequence will become more acidic. This could have consequences for marine organisms' ability to build skeletal parts. ®